Booster Rep Rate and Intensity Issues Beyond Proton Plan

1
Booster Rep Rate and Intensity Issues Beyond
Proton Plan

• Eric Prebys, FNAL Accelerator Division

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Limits to Proton Intensity

• Total proton rate from Proton Source
  (LinacBooster)
• Booster batch size
• 4-5E12 protons/batch, depending on beam quality
  requirements
• Booster repetition rate
• 15 Hz instantaneous
• Prior to shutdown 7.5Hz average (injection
  bumpRF)
• Beam loss
• Damage and/or activation of Booster components
• Above ground radiation
• Total protons accelerated in Main Injector
• Maximum main injector load
• Six slots for booster batches (3E13)
• Up to 11 with slip stacking (4.5-5.5E13)
• Possible RF stability limitations (under study)
• Cycle time
• 1.4s loading time (1/15s per booster batch)

Historically our biggest worry
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Some Numbers to Keep in Mind

• At 120 GeV, 100 kW is roughly
• 1E20 protons/year
• 1 Booster Hz _at_5E12
• 2E16 peak proton intensity out of Booster
• ABSOLUTE limit of this Proton Source
• 5E12 batches _at_ 15Hz
• 1.5MW _at_ 120 GeV
• 1.5E21 protons/year
• 3E16 pph out of Booster
• This is about 2x the present proton plan

not including prepulses.! Add 2Hz/(MI cycle) for
total rate
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Rep Rate Issues in Proton Plan

• Proton Plan Mandate
• Slip stack to NuMI and pBar
• Maintain about 2E20 protons per year to the 8 GeV
  line
• This requires the Booster to go to about 9Hz
• Identify rate limitations
• If something needs to be replaced or
  significantly modified to achieve 9Hz, do the
  incremental work to make it 15 Hz compatible.
• Identify and roughly cost out remaining issues to
  go from 9Hz to 15Hz.

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Summary Significant Elements of Proton Plan

• Linac
• Stockpile two year supply of spare 200 MHz power
  amplifier tubes (7835s), in the event of an
  interruption in supply
• Characterize and improve Low Energy Linac Low
  Level RF
• Booster
• Replace and reconfigure injection bump (ORBUMP)
  system.
• Relocate 8 GeV dump from Booster tunnel to MI-8
  transfer line
• Make Booster robust to 9 Hz, and understand
  requirements to go to 15 Hz
• Design, build, and install new corrector system
• Main Injector
• Replace seven quadrupoles with increased aperture
  versions, to reduce injection and extraction
  losses.
• Operationally develop multi-batch and multi-batch
  slip stacked operation
• Design and install collimation system, both in
  the MI-8 line and in the MI ring
• Modify injection kicker to allow multi-batch slip
  stacked operation
• Characterize and perhaps make improvements to RF
  system, to support high intensity operation.

Red to be completed this shutdown
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History of Booster Rate Limitations
solved

• MP02 extraction septum
• 2 Hz
• Replaced 2003, now 15Hz
• MP01 extraction septum
• 5Hz
• Replaced 2004, now 15 Hz
• ORBUMP magnets and power supply
• 7.5Hz
• Being replaced this shutdown -gt 15 Hz
• RF cavity drift tube cooling
• 7.5 Hz
• Installing cooling this shutdown -gt 15 Hz
• 13.8 kV transformers
• Questionable reliability at gt 7.5 Hz
• Being replaced this shutdown -gt 15 Hz
• Bottom line
• After this shutdown, Booster will be OK to 9Hz
• Done as far as the Proton Plan is concerned.

Being solved this shutdown
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Whats needed for SNuMI?

• At the end of the Proton Plan, the Booster will
  be capable of
• Peak proton rates based on beam loss of about
  1.8E17 protons per hour
• Sustained operation at 9Hz
• This will limit the actual output to 1.3E17,
  depending on the details of the supercycle.
• This roughly accommodates the baseline Nova
  recycler retasking scheme
• 11 booster batches into Recycler ever 1.4
  seconds.
• 700 kW to NuMI
• NO addition protons available for MiniBooNE,
  SciBooNE, or SY120.
• Anything beyond this will involve Booster
  modifications beyond the Proton Plan
• This includes alternative approaches to 700 kW
  involving small MI loads with a short cycle time!

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Going Beyond 9Hz

• After this shutdown, the only thing limiting the
  Booster rate will be the RF drive system.
• Half the RF bias supplies have transformers which
  would need to be upgraded.
• Significant effort and lead time.
• Cost few hundred K
• 480 distribution system
• Being investigated
• On the order of 100K to upgrade, if necessary.
• Feeder from substation
• Probably OK.
• 250K if its not
• Total cost
• Still being determined
• Of order 0.5-1M

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Beam Quality at High Intensity

• All Proton Plan projections assume slip stacking
  no more than 4E12 batches
• Although Booster capacity is speced out for 5E12
  batches.
• As the Booster goes up in intensity, the beam
  quality degrades
• Have demonstrated 6E12 batches single batch
• However, when slip stacking was implemented
  regularly in early 2005, there were problems
  related to Booster beam quality above 3.5E12
• This became one of the central issues for the
  Stacking Rapid Response Team
• Jim Steimel in charge of Booster part, working
  with booster personnel.
• See McGinnis March Review talk for details

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RRT Steps to Improve Booster Beam

• Reduction of longitudinal emittance growth at
  transition
• Quadrupole Mode 0
• Bunch Rotation at Extraction
• Longitudinal Dampers
• Dipole Mode 0, 1, 2, 52
• RF Cavity balancing
• Results

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Effect Booster Quadrupole Damper
Quad Damper on
Quad Damper off
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Future Improvements Higher Intensity

• Transverse emittance can be controlled with
  appropriate sextuple compensation
• We are building a bunch by bunch transverse
  damper system
• Lots of bunches -gt lots of bandwidth
• Sweeping delay
• New Booster corrector system will have sextupoles
  at ever subperiod (2007 and 2008)
• Other Solutions for Booster Longitudinal
  Emittance Blowup
• Gamma-t jump currently problematic
• Large orbit shift confuses cogging
• New gamma-t system will be installed along with
  correctors in 2008
• RF Step at Transition (pre-focus)
• Calculations finished look very promising
• Requires large voltage step